bind apply call code example

Example 1: call apply bind in javascript examples

Answer in SIMPLEST form

Call invokes the function and allows you to pass in arguments one by one.
Apply invokes the function and allows you to pass in arguments as an array.
Bind returns a new function, allowing you to pass in a this array and any number of arguments.

Apply vs. Call vs. Bind Examples
--------------
Call

var person1 = {firstName: 'Jon', lastName: 'Kuperman'};
var person2 = {firstName: 'Kelly', lastName: 'King'};

function say(greeting) {
    console.log(greeting + ' ' + this.firstName + ' ' + this.lastName);
}

say.call(person1, 'Hello'); // Hello Jon Kuperman
say.call(person2, 'Hello'); // Hello Kelly King

--------------
Apply

var person1 = {firstName: 'Jon', lastName: 'Kuperman'};
var person2 = {firstName: 'Kelly', lastName: 'King'};

function say(greeting) {
    console.log(greeting + ' ' + this.firstName + ' ' + this.lastName);
}

say.apply(person1, ['Hello']); // Hello Jon Kuperman
say.apply(person2, ['Hello']); // Hello Kelly King

-------------
Bind

var person1 = {firstName: 'Jon', lastName: 'Kuperman'};
var person2 = {firstName: 'Kelly', lastName: 'King'};

function say() {
    console.log('Hello ' + this.firstName + ' ' + this.lastName);
}

var sayHelloJon = say.bind(person1);
var sayHelloKelly = say.bind(person2);

sayHelloJon(); // Hello Jon Kuperman
sayHelloKelly(); // Hello Kelly King

Example 2: call apply bind

const obj = { number: 1 }

function foo() {
	console.log(this.number)
}

//bind - binds obj's 'this' context to foo, but doesn't call it
const newFoo = foo.bind(obj) 

//call/apply - binds obj's 'this' context to foo, then calls it
foo.call(obj, /*arg1*/, /*arg2*/) 
foo.apply(obj, [/*arg1*/, /*arg2*/])

//Only difference between call/apply is argument passing - ',' vs '[]'